re: Neurologist said he is considering filing with a judge to remove my FIL from his finances

If his cognitive capacity is really that bad. TODAY you should find a family lawyer and get your wife and any of her siblings together IMMEDIATELY and establish a conservatorship for your FIL. I would not hesitate on that matter if the doctor is suggesting and threatening to get a judge to do it.

There are companies out there in FL and out west that take advantage of old people with these conditions and
cut them off from family and drain finances. Better that family intervenes on this matter now than the courts.

It is best if this is a family decision with all siblings involved. Do NOT trust that doctor and find another one immediately. I cannot stress this enough. If your FIL is that far degraded, you are doing him a favor by getting involved TODAY. The parent child roles have reversed and if you love him and care about him, you NEED to do this.